Casing mill



June 3, 1952 E. J. RoBlsHAw CASING MILL 2 SHEETSr-SHEET 1 Filed July 29,1948 Ea r'/ Rob/.sha w INVENTOR.

A T TORNE Y June 3, 1952 E. J. RoBlsHAw CASING MILL 2 SHEETS-SHEET 2Filed July 29, 1948 w R. a m Mm m m J.. w 0 E birilli x f A a .M

ATTORNEY Patented June 3, 1952 cAsING MILL Earl J. Robishaw, Houston,Tex., assignor to A-l Bit & Tool Company, Houston, Tex., a corporationof Texas Application July 29, 1948, Serial No. 41,236

4 Claims.

This invention relates to a pipe cutter such as a casing mill which isparticularly adapted to be used in a well bore for cutting out a sectionof the well casing or pipe.

It is frequently desirable in connection with well operations to cut outor remove a section of the casing lining the well bore in order toprovide access to the formations along the well bore for purposes ofconducting various types of operations with respect to such formations.Heretofore various cutting tools have been designed for cutting outsections of the pipe in a well bore. These tools consist essentially ofa head, carrying laterally expandable cutting blades, which are attachedto the lower end of a string of pipe by means of which the cutting headis lowered to the desired depth in the well. The blades are thenexpanded into contactwith the casing wall and the operating pipe stringis rotated from the top of the well to cause the blades to rst sever thepipe and then to engage in a milling operation on the upper edge of thelower portion of the severed pipe in order to cut out as long a sectionof this pipe as may be desired to provide access to the surroundingformations.

Such existing tools may employ hydraulic means for expanding cuttingblades but ordinarily employ the weight of the operating pipe string forapplying pressure to the knives to effect the desired milling operationof the upper end of the severed pipe. Such conventional tools sufferfrom several disadvantages arising primarily from the employment of theweight of the operating pipe string to apply pressure to the cuttingblades. Particularly when used in deep wells, the natural ilexibility ofthe long operating pipe strings make it very difI-loult to control fromthe top of the well the weight applied to the cutting blades. Also thetorsional forces resulting from rotation of long operating pipe stringswill result in a substantial degree of twisting of the operating stringwhich again makes it difficult to maintain the proper pressure on thecutting blades. Excessive pressure will result in destruction of theblades while insufficient pressure will prevent the blades from properlycarrying out their cutting function.

The present invention has for 'its principal object the provision of acutting tool in which the pressure on the cutting blades is appliedthrough a fluid medium controlled from the surface to permit uniform andaccurate control of the applied pressure.

An important object is the provision of a cutting tool wherein thepressure applied to the cutting blades is independent of the weight orlongitudinal movement of the operating string.

A further object is the provision of a cutting tool in which fluidpressure is employed both for expanding the cutting blades and formaintaining predetermined pressure on the cutting blades during themilling operation.

A more specific object is the provision of a cutting tool employing airas the pressure fluid medium for operation of the tool.

A further object is provision of means for signaling to the operator atthe surface When the cutting blades are fully extended laterally andwhen a predetermined interval of longitudinal cutting has beencompleted.

Other and more specific advantages of this invention will becomeapparent when read in conjunction with the accompanying drawings whichillustrate a useful embodiment in accordance with this invention.

In the drawings:

Figs. 1 and 2 together constitute a longitudinal sectional View throughthe cutting tool in accordance with this invention, showing the tool inposition in a well casing prior to engaging in cutting operationsthereon; A

Fig. 3 is a view similar to Fig. 2 showing parts of the tool with thecutters engaging the casing;

Fig. 4 is a View showing the parts of the tool in another positionduring operations;

Fig. 5 is a schematic View of the well head con nections employed inoperating the tool; y

Fig. 6 is a cross-sectional view along line 6-6 of Fig. 2; and t Fig. 7is an enlarged view of a detail ofthe Referring to the drawings, thetool in accordance with this invention comprises a cutting head,indicated generally by the numeral IIJ, and

a telescoping connection, indicated generally byL the numeral I I, forconnecting the cutting head to an operating string of pipe I2 which isemployed for lowering and raising the tool in a well A' casing I3 andfor operating it in the manner to be hereinafter described. Cutting headII) is of more or less conventional construction and comably mounted onpivot pins Il for radial movement toward and away from casing I3. Foractuating the blades,` a plunger I8 is slidably mounted in the bore ofbody I4 and is normally urged up` in Fig. 2.

Telescoping connection II comprises an upper `cylinder 24, a lowercylinder and a hollow externally splined rod 25 telescopicallyconnecting the two cylinders for relative longitudinal move. ment, whilemaintaining rotative connection between the cylinders. Upper cylinder 24has` a hollow bore 21 and is provided atV its upper end with aninternally threaded socket 28 for attachment to a conventional threadedpin member on the lower `end'of operating pipe I2. A port 29opensfthrough the `wall of cylinder 24 at a point justv belowsocket`28and is closed. by an inwardly openng check valve A tubular bushing 3I iscncentrically arranged in the upper end ofY cylin. derV 24 .and lockedinposition betweenthe basleof Vsocket'28 and the inserted end of pipe I2-by means'of a radial flange 32. Bushing 3l extends somewhat below thelevel lof port 29 into bore 21. Lower cylinder 25 has a hollow lbore 33which is reduced in diameter at its lowerend to. provide a cylinder 34of smallerv diameter than bore 33..V The exterior of cylinder 34 isthreaded far'jjconnecuon to a. threaded socket a5` n the, upper end ofbody I4. Plunger I8 is adaptedrto extend into cylinder 34andhasrrnounted on its upperend a piston 3S which ca rries a resilientpacking ring 3'l'slidably engageable with the wall ofeylinder 34.

"Splined rod, 26, the exterior of which is preferably hexagonal in crosssection, but whichlnay be of any other irregular congurationhas anexternally threaded pin 3B which is adapted to Ybe:.sfcr'ewed into asocket 39 provided in thelower end offupper cylinder 24. The bore ofsocket 39. is'reduced in diameter relative to boremZ'I,ythereby'providing an internalv annular shoulderil) at the ylower. end oicylinder` 24,.v A plurality of radiali extending ports 4I open throughthe wall oi .cylinder 2 4 immediately above shoulder 4 5.

The lower end oi splinedrod 25 is slidablyenfcaged inthebore ofspline,collary 4g which `has an internal configuration complementing theex:- ternal configuration of splined rod4 26, whereby rotationalconnection between these members is. .v

maaied, While Permitting relative longitudinal movement between theseparts. The lower encf collar42 isprovided with. an externally :threadedpinl 43, for engagement in Va threaded,V

soo et M'provided at the upper end ,or Ylower cylinder 25.v The lowerend oi pin 43 forms an.` inwardly .extending shoulder 45 atA the upper;end

Selinedlfzdi vcarries a bushing ,46. havinga pacte ingring- Al nio ntedin kthe exterior thereoi-v to, thereby-.for

oilvsplined rod 25.V A plurality of radially extendilzia Orts.- 48, openthrough theV Wall oi cylinder 2.5

9. forming anA extension of plungerV4 I8,1 ex- ,Slidahle therein. Alpacking ring; .5c-is. arranged in the; bore oi pin; V38 to orm a fluiden the bov i f vfluid-iight. disable tentamen thginner Wall. of cylinder.25 and, the lower endegli,3111613 belowA the shoulderv 45. A hollow.

fxfids. axially through .the bore of, .spliced mais e fr splinedfrod 26..andiA stem 49. The lower end of stem 49 is rigidly connected to plungerI8 and is provided with a plurality of ports 5I adjacent the point ofconnection to plunger I8 to provide communication between the bore ofstem 49 and bore 33 of the lower cylinder 25. The upper end of stem 49,which extends into bore 21 of upper cylinder 2li, has mounted thereon apiston 52 (see Fig. 7) through which extend a pair of spaced passageways53 and 54. Passageway 53 is closed by an upwardly opening spring-loadedcheck valve 55 having a stem 55 which extends below the lower face ofpiston 52. Passageway 54 is closed by aspring-loaded downwardly openingcheck valve 51 having a stem 53 which extends above the upper surfaceofjpiston 52. Stem 49 is of such a length that when the telescopingconnection I I is in its fully extended position and blades IS are'inYtheir retracted position, as illustrated in Figs. l and 2, the lower endof valve stem 56 will be spaced from shoulder 45 by ardistancecorrespondingto .the length of travel of plunger stem49 required toforce blades I6 into their fully extended position, so thatwhen thatcondition is attained, lower end ofvalve stem 55 will strike shoulderk4l) and open check valve 55 (seeY Figs. 3 and 7).

Fig. 5 illustrates the arrangement of connections `at the well heademployed in the operation of the vtool in accordance with thisinvention. -It will beseen that operating pipe i2 is connected at itsupper end to the usual Kelly'joint 59 which extends through rotary table59 and is connected to a conventional rotary swivel 5I suspended A froma hook 52a. of the usual traveling block (not shown) of a drilling rig.A iiuid supply pipe 52 connects the interior of the rotary swivel to apressure uid reservoir tank 63,`which is supplied wth'suitable pressurefluid through a pipe 54 from any suitable source of supply by means of apump or compressor (not shown),- as the case.

scribed. Operating` pipe I2 carrying the cut ting Atool `connected toits lower end, will be lowered into. the well and connected forrotation, by` rotary table 50 in the ,usual manner, as

illustrated in Fig. 5. When entering casing I3. the. parts,V of thevtoolgwill be in the positions illustrated in Figs.v l and 2particularly, that is, blades -Ie will be retracted and telescopingconnection II willbe in its extended position, the

weight of the cutter `head Ybeing suiiicient nor. mally to fullyextendrthe connection. Piston 521 atf.the. upper vend of the plungerstern 49 will beheld in the4 upper position illustrated in;Fig It willVVbe assumedinthis example thatl no extraneous iiuid, such as drillingmud orwelliiuid,ispres--aY ent. incasing I3. Whenthe cuttersv-havebeen:

l bythe upward thrust ofcoil spring I9.

lowered to the point at which cutting ofthe casing. is. to begin, therotation of theoperating pipe will be started and iluid pressure; whichin this.v example mayA be airv pressure, vwill be supplied4 Ythroughthev surface*v4 connection-s tothe interior ofi, theoperatinggfpipestring. The plesf sure fluid, which will be suppliedfrompipefbv; way 0f. reservoir 53. under the .control-.or res- Apressureulator 65, will enter cylinder 24, and flow into y the bore ofextension rod 49 and thence through ports into the interior of cylinder25. The loading of check valve 51 will have been preset to hold thisvalve closed against the predetermined operating pressure. The pressurewill thus be applied to theupper faces of pistons 52 and 36, forcingplunger I8 and itsextension rod 49 downwardly against the resistance ofspring I9, causing expansion of blades I6 into cutting position againstthe casing. Rotation of p ipe'string I2 will rotate the cutter body byreason of the splined connection formed between spline collar 42 andsplined rod 26. As the operating string rotates, blades |6 will cut intothe wall of casing I3, being forced outwardly under the pressure appliedto pistons 36 and 52, which move downwardly as the blades continue toex-A pand. When the blades have severed the casing, they will attain thehorizontal position illustrated in Fig. 3 and, as noted previously, byreason of predetermined dimensional relationship, the lower end of valvestem 5B will, at that instant, come into contact with shoulder 40forcing check valve 55 to open, relieving the pressure from inside bore21 through passageway 53 and ports 4I into the annular space between thetool and casing I3. This produces an instantaneous drop in pressure inthe interior of the tool string which will be indicated at the surfaceon gage 68 and will constitute a signal to the operator that the casinghas been severed.

The operations for milling the severed casing may now be begun. Theoperating string will be lowered by lowering hook 62a in the usualmanner for a distance suiicient to collapse telescoping joint II. Thismay occur because body I4, lower cylinder 25 and splined collar 42 willbe supported against downward movement by the residence of the nowextended blades I6 on the upper edge of the lower portion of the severedcasing (see Fig. 3), thereby allowing upper cylinder 24 and splined rod26 to move downwardly relative thereto. As upper cylinder 24 and splinedrod 26 move downwardly, piston 52 will, of course, remain stationary andshoulder 40 will move downwardly relative thereto and release valve stem56 allowing check valve 55 to close. This permits the pressure abovepistons 52 and 36 to again build up to the operating level. The parts ofthe telescoping connection I I will be so dimensioned, that when theconnection is fully collapsed, the upper end of valve stem 58 willstrike against the lower end of bushing 3|, opening check valve 5l andagain venting the pressure fluid through ports 4| (see Fig. 4). Thiswill again be indicated by a drop in the pressure on gage 68 and will bea signal to the operator that the splined connection is fully collapsed.This is important because it will enable the operator to know instantlywhen to stop the lowering movement of the operating pipe so as to avoidthe application of its weight to the blades, and thereby avoid thedamaging effect thereon of excess weight. The operator will thenimmediately lift the operating string just sufficiently to permit valve51 to close by the action of its loading spring, whereupon the pressurewill again be allowed to build up to the desired operating level fromtank 63 through regulator 65. With the pressure now built up, rotationof the operating string is continued while the upper end of theoperating string is held stationary against longitudinal movement.

WithY the pressure thus applied to pistons52 and 36, the blades willproceed to mill off the upper end of the severed portion of the casing.With operating pressure being maintained at the desired level duringthis operation, as the upper end of the lower casing section is thusmilled off,V the cutter head and cylinder 250iv the telescopingconnection will descend, extension 49 carrying piston 52 descendingcorrespondingly as thev telescoping connection becomes extended. Themovement of these parts relative to upper cylinder 24 and pipe I2 willcontinue until piston 52 has descended in cylinder 24 to a, point atwhich stem 56 again strikes shoulder 40 whereupon valve 55 will beopened and the pressure relieved through ports 4I. This will immediatelyapprise the operator at the surface, through the deflection of theindicator on gage 68, that the telescoping connection has become fullyextended. Since the length of movement of the telescoping connection isknown, the operator will be apprised that a corresponding length of thesevered section of the casing has been milled 01T. If an additionalincrement of the casing is to be milled off, the operator willimmediately lower the operating string until valve stem 58 strikesbushing 3|, again signaling the full retractionof the telescopingconnection and apprising the operator that the tool is ready for arepetition of the previously described operation for continuing themilling of the casing. This operation may be repeated as often asnecessary to cut out a section of the casing of the desired length. Whenthe milling operation has thus been completed, the iluid pressure isrelieved at the surface by opening valve '10. The operating string islifted at the surface raising blade I6 above the upper edge of thesevered portion of the casing, thereby allowing coil spring |9`to forcepiston I8 upwardly and retract blades I6, whereby the entire string maybe withdrawn from the well.

It will be understood that instead of air as the pressure iluid employedin the above operation, hydraulic fluids may be employed for the samepurpose. as well as other pneumatic fluids, such as natural gas and thelike. The uid pressuresV employed may be varied to suit particularconditions which may be encountered. Ordinarily pressures of about200-300 pounds per square inch will be sufficient for most purposes.Likewise the length of travel of telescoping connection I may be variedas desired, with one to three feet being convenient lengths for mostpurposes.

Where liquid is present in the well, such as ordinary drilling mud orwell fluids, ports 29, 4| and 48 provide means for transference of suchuids between the interior and exterior of the tool string to permitsuitable equalization of the pressures, while air pressure is suppliedfrom the surface for operation of the tool. The operation will besubstantially the same, the air acting on the liquid inside the toolstring in the manner, as previously described to control the cuttingoperations.

From the foregoing it will be seen that with a cutting tool constructedin accordance with this invention, fluid pressure is employed not onlyto expand the cutting blades for severing the casing but also to controlthe milling pressure applied to the blades. The pressure fluids thusafford very convenient and accurate means for maintaining very closecontrol of the pressures to be applied and thereby permit very accuratecontrol of the cutting operations with minimum danger of damfocaccetlienovelconstruction of the tool,` including thev described Signallingarrangement, enables theoperator'to determineiwitha'high degree offer"-Yactitude the length Vof Vcasing or other f well pipe which; i-S rlvd by'the tool.

It 4Will b understood that variousl Vchangesand valterations may be madeinthe details 'of the embodiment herein described'wthot departing fromthe scope of'the appended claimsv but Ywith inthe spirit of v thisinvention.V

What-I anim and desire `'to secure by Letters Patent is:

l. A vcasing mill, comprising, a head carryingradiallyexpandible'cutting blades, ahollow telescoping coupling memberfor connecting said head member with an operating pipe, said couplingmember includingv a pair of end-aligned cylinders arranged ,for relativelongitudinal movement and a hollow spline member connecting saidcylinders for said relative longitudinal movement while maintainingrotative connections therebetween, a hollow plunger having a boreaffording communication for movement of-pressure'fluid between saidcylinders slidable axiallyof said spline member,l pistonsmounted on theplungerand located in said cylinders, said plunger.

being connected "to said blades and said head member and actuable solelyby fluid pressure transmitted through said pipe to expand said bladesand to advance said'head member-relative to said operating pipe, spacedopenings in f said plunger communicating Awith 'the respectivecylinders, and valve means carried by said plungver jactuable-'byengagement thereof with eitherv of saidfstop" 4orleans vto produce adropv inthe iiuid pressure applied to said plunger means.

y3. Afcasmg-miu, comprising, a head-member' carrying radially*expandible cutting blades, ja' hollow telescopig coupling member forconnect: ingsa'id headimember to an operating-pipe, said couplingvmember including-'af pair "of endl-aligned cylinders anda hollow splineniembericonnecting said cylindersfor relative longitudinal movementwhile f maintaining rotative'v connection th'erebe# tween,hollowfplunger means slidable aiiiallyv of" said coupling member andvaffording pressure'lluid communication between ,said cylinders'i saidplunger means being connected to4v saidblades and said headandactuablejsolelyr by fluidpress'ilrelto expand saidblades and to advancesaid headmember'relative to said operating-pipe, a'sealing'pistonxnounted onis'aid plunger means for slid er foi-'controlling themovement fofr pressure fluid therebetween, Ahollow plunger meansslida'ble'axially offsai'd coupling member' and affording pres-Y sfireiiuid communication between said cylin derssaid plunger 'means-being,connected to ,said

blades; and actuable solely by fluid pressureto Y eii'pandsaid bladesand to. advance. said.` head nieinber'relativeV to. operating 'pipefcooperating stop means. arranged betweensaid plunger means and saidvcoupling',v member to limit felaing movement therewith inthe upper'on'eof said cylinders, spaced stop members in said upper cyl' inderon'lopposite'sides of 'said piston, passage ways throughthe wall of saiduppery cylinder-be-v low thepoint of maximum descent of said piston,normally closed valve means carriedby saidrpis ton and e' aotuable byengagement with either'of said stop menibersto be opened for thedischarge of pressuref'fluid from above said piston throughsaidpassageway.

4. A. casing'r mill, comprising, ahead member carrying radiallyexpandible vcutting blades.V a hollow telescopingcoupling member forconnecting said head member to an operating pipe,` said coupling memberincluding apair of end-aligned cylinders andaV hollow spline memberconnecting said cylinders for' relative'longitudinal movement whilemaintaining rotative'connection therebetween, lplunger means slidableaxially of said spline member and connected 'at'its lower end to saidvblades for expanding said blades and for advancing` said head memberrelativev to'fsaid opf-V erating'pipe, 'a bore in said plunger affordingpresi' sure fluid communication between saidr cylinders, pistons mountedon` saidV plunger in each'of Asaid cylinders forming slidablefsealstherewith, and

NtmerV f--u Nov. l., 1938 Conner gena-...is ct.v 20", 1942

